The present invention relates to a method and apparatus for excavating a trench and more, particularly for excavating a trench having an obstacle extending along one side thereof.
When assembling an underground pipeline a trench is typically first excavated wherein the excavated dirt from the trench is piled along one side the trench. The pipeline may then be assembled above ground along the other side of the trench opposite the excavated dirt. Once the pipeline has been assembled various lifting equipment is used to place the pipeline into the trench as the equipment is displaced in a longitudinal direction of the trench.
Typically when laying the pipeline into the trench, further excavation of the trench is required to remove water and dirt which has accumulated in the trench while the pipeline was assembled. Conventional hydraulic excavating equipment cannot be used however as typical backhoes and the like are not able to reach over the pipeline into the trench once the pipeline has been assembled. The use of a crane having a cable operated bucket is thus known to be used. Cranes however are difficult to guide and typically require a second operator located near the trench to guide the bucket. Furthermore operators of such equipment are difficult less common than operators of modern conventional hydraulic excavating equipment.
According to one aspect of the present invention there is provided a method of excavating a trench having a pipeline extending in a longitudinal direction of the trench along one side of the trench, the method comprising:
providing an excavator having a base supported for movement across the ground in a forward working direction, an extension arm mounted on the base, a lift arm pivotally mounted on the extension arm for pivotal movement about an upright axis, a working arm pivotally mounted on the lift arm for pivotal movement about a generally horizontal axis and an excavating bucket mounted on a free end of the working arm;
locating the excavator on one side of the pipeline opposite the trench with the forward working direction being oriented generally parallel to the longitudinal direction of the trench;
positioning the extension arm to extend from the base laterally over the pipeline transversely to the forward direction;
pivoting the lift arm in relation to the extension arm until the excavating bucket is aligned with the trench;
lowering the excavating bucket into the trench; and
excavating earth from the trench using the excavating bucket.
The present invention provides a hydraulic arm which can be operated similarly to conventional hydraulic equipment. The articulations of the arm about a generally horizontal axis as well as an upright axis permit the arm to be aligned with the trench when reaching over a pipeline without the need to rotate the base of the excavator which is positioned adjacent the pipeline in use to prevent possible damage to the pipeline.
The method preferably includes displacing the excavator in the forward working direction alongside the pipeline.
Preferably the method also includes dumping the earth excavated from the trench along a side of the trench opposite the pipeline.
It is preferred that the excavating. bucket comprise a clam bucket having a pair of confronting shovels. In this instance the method may include providing a hydraulic operating mechanism for controlling the bucket and actuating the hydraulic operating mechanism to excavate earth from the trench.
The excavator may include an operator cab on the base having a lift mechanism arranged to displace the cab in relation to the base with the method including raising the cab upwardly over the pipeline and the extension arm. The method may further include raising the cab laterally outwards over the pipeline towards the trench.
The method preferably includes restricting displacement of the extension arm as the lift arm is pivoted to align the excavating bucket with the trench.
A water pump may be arranged to pump standing water from the trench wherein the method includes grasping the water pump with the excavating bucket, lowering the water pump into the trench and pumping water from the trench.
The method may further include locating the water pump on the base, pivoting the lift arm to extend laterally inwardly toward the base and grasping the water pump on the base with the excavating bucket.
According to a further aspect of the present invention there is provided an excavator comprising:
a base supported for movement across the ground in a forward direction;
an extension arm mounted on the base, the extension arm being arranged to extend from the base transversely to the forward direction to an outer end spaced laterally outward from the base in a working position of the extension arm;
a lift arm mounted on the outer end of the extension arm for pivotal movement about an upright axis relative to the extension arm;
a working arm pivotally. mounted on the lift arm for pivotal movement about a generally horizontal axis relative to the lift arm; and
a clam bucket mounted on a free end of the working arm, the clam bucket comprising first and second confronting shovels mounted for pivotal movement relative to one another between an open position in which the shovels are spaced apart and a closed position in which the shovels are located adjacent one another.
The combination of a hydraulic clam bucket with the articulated hydraulic arm described herein is particularly useful for excavating earth at a location spaced laterally from the vehicle on the opposite side of an obstacle, for example a pipeline. The clam bucket does not impose any excessive moments on the hydraulic arm supporting the bucket when digging into the earth as does a shovel-type bucket which is typically found on excavating equipment including backhoes and the like.
A hydraulic operating mechanism is preferably coupled to the clam bucket arranged to displace the shovels between the respective open and closed positions.
The clam bucket may be supported on the working arm for rotation about an upright axis through a range of 360 degrees of rotation.
The lift arm and working arm are preferably arranged to extend inwardly across the base with the clam bucket engaged on the base in a storage position.
In this instance there may be provided a water pump supported on the base such that the clam bucket is arranged to engage the water pump to be displaced by the lift arm and working arm.
The lift arm may be pivotal relative to the extension arm about the upright axis through a range of at least 300 degrees of rotation, but preferably through a range of 360 degrees of rotation.
There may be provided an operator cab supported on the base having a lift mechanism arranged to displace the cab in relation to the base upwardly and laterally outwardly in relation to the base.
The extension arm may be arranged to extend substantially horizontally outward from the base in the working position.
There may be provided a pivot base mounting the lift arm thereon for pivotal movement about the upright axis, the pivot base being supported on the extension arm for pivotal movement about a generally horizontal axis.